Asbestos yarn and method of production



Dec. 18, 1951 l. J. NOVAK ETAL 2,578,941

ASBESTOS YARN AND METHOD OF PRODUCTION Filed April 28, 1949 2 SHEETS-SHEET 1 ZEW/e n fora. jiador Jf/a z//l lz'fford 11/. j alm Dec. 18, 1951 1. J. NOVAK ETAL 2,578,941

ASBESTOS YARN AND METHOD OF PRODUCTION Filed April 28, 1949 2 SHEETS-SHEET 2 lhi/nzonsi' 1200 07" Jt/vfak Clifford [([Pa Zm Patented Dec. 18, 1951 ASBESTOS YARN AND METHOD OF PRODUCTION Izador J. Novak, Trumbull, Conn., and Clifford W. Palm, Manheim, Pa., assignors to Raybestos- Manhattan, Ino., Passaic, N. 'J.;'1a corporation of New Jersey Application April 28, 1949, Serial No. 90,288

1 Claims.

This invention relates to a novel method for the production of asbestos yarn.

This invention more particularly relates to the production of fine level asbestos yarns of a relatively smooth and even surface character, and which may be of a relatively thin nature and at the same time have high tensile strength, and which may be woven, braided, knitted, twisted, etc., to produce asbestos fabrics of a character and fineness heretofore desired but generally unattainable.

This invention further relates to a novel method for the production of asbestos yarns wherein all of the fibrous material may be asbestos, without requirement for incorporation of other fibrous materials such as cotton, rayon, and the like presently incorporated in asbestos yarns as spinning aids, and to increase strength.

This invention further relates to a novel meth-,

od for the production of asbestos yarn whereby carding of asbestos fibers to produce rovings for spinning, and the time, material losses, fiber expense, and extensive equipment previously required may be avoided by employing, as the material to be spun, certain of the products prepared in accordance with the asbestos dispersion process generally described in the co-pending application of I. J. Novak, Serial No. 66,552, filed December 21, 1948, and as will be hereinafter more fully set forth.

The invention further relates to a novel method for producing asbestos yarn by spinning tapes of certain plastic, stretchable, waxy or lubricated character, and produced from tissue-like webs of long fiber asbestos dispersions made in accordance with said Novak application and wherein the fibers are yieldably bonded by subjecting said tapes, in normally dry condition, to rearrangement and intermingling of the component fibers in the web while simultaneously twisting such rearranged web material to increase the strength of the resulting yarn and to provide it with a true textile twist, similar to that obtained in twisting rovings of textile fibers, such as cotton, rayon or wool in a conventional spinning operation.

It is recognized that it has heretofore been proposed to spin tapes composed of short asbestos or paper fibers and binders in a moistened condition. Such proposals, however, did not prove to be commercially feasible due to the inherent weakness of tapes composed of short fibers, the necessity for and difficulties of moisture control, and at best such prior practices resulted in mere furling of the tapes since they were of low 2 tensile strength, particularly when moistened. and not capable of being drafted, without rupture, or, at least, edge tearing, and thus could not provide true yarns.

As distinguished from the foregoing, it is now possible in accordance with the present invention to truly spin tapes in normally dry condition composed of spinning length asbestos fibers, and to produce thereby smooth, level, fine, asbestos yarns of novel character, all in an economical manner and at spindle speeds much higher than the heretofore conventional asbestos spinning practice. One of the reasons; for the present ability to spin asbestos tapes is that the aforesaid Novak asbestos dispersion process makes it feasible, for the first time, to prepare wet-felted papers and tissues from the: long or spinning grade asbestos fibers, of a smooth dense nature, free of entangled fibrous clumps or clots with the fibers highly directionalized in the machine direction. Another of the reasons is due to the employment and incorporation of certain organic surface-active agents in the dispersion process which are of a waxy or unctuous nature, providing the paper or tissue product with a binder which gives the paper a plastic character and permits appreciable stretch, distortion, and slippage of the fibers, before rupture.

Thus, and in accordance with the preferred practice of the present invention, we employ in the spinning step, to be subsequently described, tapes of about A to inch in width, slit from tissue-like webs of asbestos having a thickness of from about,.0002 to about .0015 inch, formed on a paper-making machine from individualized and dispersed spinning length chrysotile asbestos fibers, as is generally described in the aforesaid Novak application. This web material is dense and porous, is soft and pliable and has drape," and is further characterized by being predominantly composed of individual or "unit" fibers having a diameter of from about 200 to 500 Angstroms, the fibers having organic surface-active agent adsorbed thereon and the sheet or web material containing an additional relatively small quantity of free surface-active agent, with the asbestos fibersthereof highly oriented in the machine direction. These webs may contain on the order of from about 3% to about 6% by weight total organic surface-active agent, of which approximately 10% to 30% is free and removable and 90% to is adsorbed and fixed to the fibers in what appears to be a physicalchemical relationship.

Although the aforesaid Novak application deabout 10% to about 30% before rupture, while I maintaining a minimum modulus of strength of the order of 25 pounds per square inch, so that the tapes may be held under tension during the spinning operation and the fibers permitted to slide on one another to become not only more fully oriented in a direction longitudinally of the tape being spun, but more particularly to become intermingled and thereby readily take on and retain a true textile twist. g

, Tissues having such properties are those prepared by employin as the dispersing agent such surface-active agents as dioctyl ester of sodium sulfosuccinate (Aerosol 0T); sodium sulfate derivative of 3, 9, diethyl tridecanol 6 (Tergitol T) alkanolamine salt of sulfated alcohol (Emcol X-25); sodium trialkylsulfotricarballylate (Nekal NS); dibutyl triethylene oxide benzene sulfate (Triton 7'70); dibutyl triethylene oxide benzene sulfonate (Triton 720); sodium ethylene sulfonate oleate (Igepon AP); and others. These are to be distingui hed from other asbestos dispersing agents such as the soaps, sodium oleate; sodium stearate; sodium linoleate; dodecyl benzene sulfonate (Santomerse 3); sodium lauryl alcohol sulfate (Orvus WA); keryl benzene sulfonate (Nacconal NR); oleyl alcohol sulfate (Duoonol LS); and polyalkyl benzene sulfonate (Ultrawet E), which give tissues which when dry have very low stretch and wherein the fibers have a relatively firm bond and adhere strongly to one another. The latter do not spin at all well when dry but can be handled fairly well by dampening sufliciently to soften residual soap and reduce the bond between the fibers thereby, and cause the sheet to take on desirable stretchablecharacter, and thus to the extent that such firmly bonded tissues require moistening they are not fully equivalent to the tissues of the first described class which are of a plastic character in the normally dry state.

The term "spinning grade fibers refers to those known as #1 and #2 crude grades and the #3 grades of mill fibers, in accordance with Canadian Chrysotile asbestos classification, and as set forth for example in Bulletin 403 of the U. S. Dept. of Interior, Bureau of Mines, entitled Asbestos. The #3F and #2 crude grades have been found to be particularly suitable for the present purpose. The asbestos tissue-like web or sheet used as the raw material in carrying out the present invention may be produced by sheeting an aqueous dispersion of asbestos of the hereinbefore indicated spinning grades, wherein the fibers have been opened, separated and individualized by subjecting macroscopic bundles or aggregates of asbestos to reaction with an agent effective to bring about such opening and individualizing in accordance with the aforesaid Novak application. One method of individualizing such bundles of asbestos comprises reacting ,the asbestos with an aqueous solution of Aerosol OT. The dispersion thus formed may be felted on a conventional paper-making machine or ex.-

truded, care being taken to insure that the fibers are oriented and parallelized.

For the purpose of illustration, and not limitation, the following is a typical example of a method of preparing long fiber asbestos tissue in accordance with the aforementioned Novak application.

A slurry was prepared as follows for making asbestos tissue. To 1000 gallons of water was added 312 lbs. of Aerosol OT in water and dissolved, then 212 lbs. of 3R spinning grade asbestos was added which on stirring for four hours produced a smooth slurry at 2 /2% asbestos concentration. This was further diluted by adding water slowly to the 2%% slurry in the volume proportion of 9 parts of 2/z%'siurry to 4'7 parts water. This produced a smooth dispersion on mixing for four hours. It had a freeness of 70,000 seconds on a Williams freeness tester. The slurry thus made. after screenin to remove associated impurities, such as serpentine fragments, magnetite inclusions or other clotswhich do not or are not adequately opened, was run on a Fourdrinier tissue paper machine at 85 ft. er

minute, and a tissue was made weighing 0.7 gram per sq. ft., about .00035 inch thick. This tissue was well formed, smooth, uniform in fiber distribution, tough, strong, stretchy, and highly oriented in the machine direction. It contained about 5% organic matter from the Aerosol OT which was divided into 4.5% adsorbed and 0.5% free residue resulting from the evaporation of the aerosol solution accompanying the fiber in the wet web as it met the dryer. This tissue is particularly adaptable for spinning into fine, high-asbestos-content yarn, because of its slight hygroscopic nature and stretchiness.

The foregoing tissue-like web material was then slit in the machine directioninto tapes of 0.25 inch in width, wound up on spools and was ready for spinning on a generally conventional spinning machine such as a Ring Frame" with or without employment of the usual drafting ope ation of the present invention, whereinrolls, as will be hereinafter more fully described in connection with the accompanying diagrammatic drawings, wherein:

Figures 1, 2 and 3 are respectively a top plan view. a front elevational view, and a side elevational view of a portion of a Ring Frame spinning machine illustrating one method of spinning in accordance with the present invention.

Figure 4 is a view similar to that of Figure 2, and Figure 5 is a fragmentary view similar to that of Figure 3, illustrating a modified arrangement of apparatus.

Figure 6 is a view similar to that of Figure 3, illustrating another modification.

Figure 7 is an enlarged perspective view of a portion of the apparatus and spinning operation shown in Figures 1 to'6.

Figure 8 is a further enlarged perspective detail illustrating a characterizing step in the method of spinning in accordance with the present invention.

As previously indicated, the apparatus which we employ in the practice of the present invention is of a generally conventional type and is operated in conventional manner well known to those skilled in the art, and we have therefore diagrammatically illustrated, and will describe only those components necessary to an understanding of the present invention.

Referring to the drawings, Figures 1 tot! illustrate one method for carrying out the spinning draiting is accomplished by employment of a conventional Ring Frame" spinning machine, but Tithout necessarily resorting to conventional dra;,ting, or employing the conventional bank of drafting rolls. Thus, the asbestos tape III of the character previously described is supplied from one or more cheeses on the Jack spool II and led. directly therefrom to and between the driven rolls l2--l2 which may be the conventional front rolls of a drafting unit. At this point and immediately in front of the rolls l2l2, as will hereinafter be more fully described, the component fibers of the tape become converged and rearranged. and the rearranged fibrous material then passes through the thread guide I! on the axis of the bobbin ll mounted on the spindle 2| and through the traveller riding on the ring it carried by the ring rail i1, and is twisted and wound on the bobbin ll by the joint rapid rotation and difference in speed of the traveller and bobbin. As is conventional, the traveller l5, revolving about the ring It, introduces twist into the'rearranged fibers of tape I substantially up to the bite of the rolls [2-42 and, because the traveller is revolving around the ring at a surface speed in excess of the surface speed of the bobbin (although at a lower R. P. M.), it winds the resulting yarn onto the bobbin. In accordance with the present invention, the relationship between the speeds of the rolls l2l2 and the bobbin I4 is such as to place the tape under appreciable tension. Although there is no precise way to measure this tension, in conventional spinning, it is judged between a condition where the ends break and one where they are slack enough to clot and snarl at the top of the flyer or traveller. In conventional spinning of cotton or wool rovings. the rovings take the twist readily because of the types and conditions of the fibers and their generally longitudinal arrangement in the fiber mass and without drafting or elongation in front of the delivery rolls. As distinguished from this, by employing and delivering the long-fiber plastic and stretchable asbestos tape of the present invention in fiat form from the delivery rolls and because of its peculiarly inherent make-up and character, it can be and certain portions of it are placed under appreciable tension so as to attenuate it between the delivery rolls and the traveller to cause the fibers at and adjacent to the lateral edges of the tape to slide on one another and to converge and rearrange themselves in the tape whereby to impart to the web material and the resultant yarn a true textile twist.

As illustrated in the enlarged detail of Figure 8, as the tape leaves the bite of the rolls i2-l2 it is still in tape form, and as twist is inserted and works back toward the roll bite, the tape at that point takes the shape of a triangle whose base is at the roll bite and whose apex is at the point of twist. From this, it can be deduced that, since the sides of a triangle are necessarily greater than its altitude, the fibers on the outer edges must necessarily slide on one another, thus causing a drafting of the fibers on the edges of the tape. This attenuation not only brings about further directionalization of the fibers longitudinally of the tape, but displaces them from Further reference to the detail of Figure 8 will make it apparent that all points on the tape on the line of contact between the feed rolls are equidistant from a line drawn through the point of twist and parallel to the line of contact between the feed rolls. Assuming that the midpoint or longitudinal axis of the tape at the moment it leaves the contact between the feed rolls is on a line passing through the point of twist and perpendicular to the line of contact betweenthe feed rolls, then such a point on the tape moves forward a distance equivalent to the altitude of the triangle. At the same time, the points on the edges of the tape have travelled a distance equivalent to the length of the sides of this triangle. This indicates that there must have been stretching, elongation, and slippage of one fiber over another on the edge portions of the tape and similarly to a graduated degree or convergence from said edges to the center of the tape. This phenomenon is considered to be of utmost importance in t:e spinning operation of the present invention because, in the absence thereof, there would merely result a wrap or furl instead of true twist. Thus, the present invention permits for the first time the production of fine yarns from a fiat tape composed essentially of a natural mineral fiber, by modification of the character of the tape between the delivery rolls and the traveller. The tension between the delivery rolls and the traveller is regulated so that the triangle at the nip of the roll is always an isosceles triangle but many times may become equilateral, so that at all times the length of the sides of the triangle is greater than that of its altitude. The tension is further maintained to a degree such that, while the sides of the tape in the triangle formation thereof are under tension, tension on the longitudinal axis oi: the tape or altitude of the triangle is of a relatively minor order and only necessary to efi'ect the carrying out of the twisting operation.

If desired, the tape may to advantage be subjected to stretching or conventional drafting before rearranging and converging the fibers thereof between the feed rolls and traveller, as hereinbefore described. Thus, Figures 4 and 5 illustrate the employment of a driven jack spool drum l8 operating against the spool ll so as to cause the tape to be placed under tension between the spool H and the driven feed rolls 12-42. In a similar manner, Figure 6 illustrates the employment of a conventional drafting roll unit comprising conventional front or delivery rolls l2--I2 and one or more sets of rolls, driven at different speeds as well known in the art, such as, for example, the rolls l9--l9 and 20-20. Due to the stretchable and lubricated nature of the tape employed in the present invention, it may be subjected to appreciable attenuation which serves to better orient and directionalize the component fibers longitudinally of the tape and to increase the ultimate tensile strength of the resulting yarn by employing additional or conventional drafting in back of the feed rolls Ii -l2. Thus, for example, as shown in the following tables, by drafting one of the tapes of the present invention 17.8% between the spool II and the front rolls l2-i2, as in Figures 4 and 5, there resulted an increase from about 12% to 31% in the tensile strength of the ultimate yarn 'over that of the same weight or made from tape which was not previously drafted in back of the delivery rolls.

The remaining operation of spinning by simultaneous fiber rearrangement and twisting between the delivery rolls l2--l2 and the traveller 7.. is generally the same as that described with respect to Figures 1 and 3 and is generically illustrated by the perspective view of Figure 7.

After the yarn has been formed in accordance with the foregoing, it may be further strengthened by subjecting the organic material content thereof to decomposition by pyrolysis. This reduces the plastic, unctuous, stretchable. hygroscopic character of the yarn to a relatively nonplastic, firmly bonded one with increasedtensile strength having good elasticity, a novel and useful characteristic for an all-asbestos fiber yarn. In order to obtain the fullest advantage of this curing action by heat, the temperature may be between that of saturated steam at atmospheric pressure (212 F.) and the temperature at which asbestos fiber begins to lose water of crystallization rapidly, say 700 F. Higher temperatures than this may also be employed, if the time of exposure is short enough to avoid damag the asbestos fiber. With Aerosol CT, the temperature is preferably that at which it just begins to decompose or volatilize. Thus, for example, yarn prepared in accordance with the present invention from web material made from an Aerosol OT dispersion of asbestos may be increased approximately 100% to 200% in tensile strength by heating it for about three hours at a temperature of about 400-450 F. r

The practice of the present invention permits employment of spindle speeds up to about 6,000 B. P. M. and which are comparable to cotton spinning. as distinguished from the limitation in spindle speeds to about 1,700 B. P. M. when making yarn by heretofore conventional methods from asbestos rovings. Further, the practice of the present invention has permitted the "down time" or interruption of operation due to breaks in the material being spun to be reduced to the order of 5%, as distinguished from a "down time of common to the prior asbestos yarn spinning operations.

As a further comparison with prior asbestos spinning practice, a tape of the character herein ydsJlb.) -cut 100 yarn. This yarn was equivalent in strength (after heat cure) to the conventional 35-0111; yarn wherein the asbestos fiber was all #1 and #2 crude, a. grade which sells at present for twice the price of #3R fibers.

Moreover, we have been able to make 200-cut yarn composed of #3F fiber ,by the practice of the present invention.

The following tables are illustrative examples of the properties of yarn formed in accordance with the method of the present invention, results being in each case the average of a number of tests. v

The following Table I illustrates the property of yarn prepared from the felted, fibrous web of #2 crude asbestos prepared and dispersed by employment of Aerosol OT in the manner hereinbefore described, the web being of a thickness of .0005 inch and slit to produce tapes having a width of A inch. The determinations in column 1 were made on yarn produced from tape which had not been subjected to drafting and only by means of apparatus in accordance with Figures 1 to 3. The determinations in column 2 were made on yarn which had been subjected to drafting between the rolls l2-l2 and the jack spool and jack spool drum as in Figures 4 and 5. The determinations in column 3 were made on yarn which had been subjected to drafting by means of conventional drafting rolls as generally illustrated in Figure 6. The indicated cure is carried out by heating the final yarn at a temperature of 435 F. for three hours.

Table I No Draft- Dmfting Drafting ing 17 a 24.8%

Determination-Average:

Out 66.3 68.0 66.0 0.0106 0. 0114 0.11103 10.4 19.6' 19.7 Contraction, Per Cent 8.6 10. 27 8.6 Before Cure:

Tensile Strength Oz.) 16.33 13.68 14. 64 Elgngation, Per ent 4. 6. 60 6.6 r um: Tensile Strength Oz.) 26.33 29. 67 31.71 Elongation Per ent 4.4 4.0 3.4 Per Cent Tensile Strength Increase 0 Over Uncnred 71.6 118 116.6 Per Cent Tensile Strength Increase, Drafted Over Undrafted in Cured Condlflnn i 12.3 21.4

The following Table II illustrates the property of yarn prepared from the felted, fibrous web of #311. spirming grade fiber prepared and dispersed by employment of Aerosol CT in the manner hereinbefore described, the web being of a thickness of .0005 inch and slit to produce tapes havn a width of inch. The determinations in column 1 were made on yam produced from tape which had not been subjected to drafting and only by means of apparatus in accordance with Figures 1 to '3. The determinations in column 2 were made on yarn which had been subjected to drafting between rolls 12-12 and the jack spool and jack spool drum as in Figures 4 and 5.

The following Table III illustrates the property of yarn prepared from the felted, fibrous web of #3F spinning grade fiber prepared and dispersed by employment of Aerosol OT in the manner hereinbefore described, the web being of a thickness of .00045 inch and slit to produce tapes having a width of inch. The determinations in column 1 were made on yarn produced from tape which had not been subject to drafting and only by means of apparatus in accordance with Figures 1 to 3. The determinations in column 2 were made on yarn which had been subjected to draftlag between rolls II-II and the jack spool and jack spool drum as in Figures 4 and 5.

Table III Drafting 8.8

Determination-Average:

Cut

3 a as as As a non-fully equivalent alternative, we may employ tapes prepared from asbestos dispersions in accordance with the aforesaid Novak application, prepared with such dispersing agents as sodium oleate, and others previously described, which result in a firmly bonded type structure. By a "firmly bonded type" structure is meant little, if any, stretch character in the normally dry state. Tapes slit from sheets of this firmly bonded type tissue may, however, be successfully employed in the hereinbefore described concomitant fiber rearrangement and twisting step of spinning if the tapes are moistened prior to spinning and if proper care and control is exercised in the moistening of the tape so as to impart to it the ability to stretch. This is entirely feasible when employing tapes composed of spinning grade asebestos fibers prepared in accordance with the aforesaid Novak application.

As a further non-fully equivalent alternative to make yarns where the yarn shape or bulk rather than strength is required, we may employ tapes slit from tissue prepared in accordance with the aforesaid Novak application of the plastic or yieldably bonded type, that is, when employing webs of spinning grade length fibers, they are nevertheless adapted for spinning by the hereinbefore described method by reason of their plastic and stretchable character.

As another non-fully equivalent alternative, we may employ tapes prepared by casting or extrusion processes as described in the aforesaid Novak application, cast or extruded directly in suitable tape width or cut from wider sheets prepared by the casting or extrusion processes. Tapes prepared in this manner may be of a thickness substantially equal to that prepared on a paper making wire, but these casting and extrusion processes are resorted to when it is desired to prepare sheets or tapes which are of a thicker nature than it is ordinarily possible to make on the paper making wire. On the other hand, materials prepared by the extrusion and casting processes may not be as fully desirable as those made on a paper making wire since the former are generally dried by the evaporation 10 7 resulting in retention of relatively high portions of dispersing agents, such as approximately 35% to 50% by weight of the sheet (before partial destruction or removal by heat or otherwise),

as distinguished from retention of minimum amounts of dispersing agent characteristic of the dispersing liquid by filtration on a paper making wire. Further, such extruded or cast materials do not have their fibers as fully oriented in the direction of extrusion or casting or longitudinally. and therefore not as suitable as the highly directionalized material produced on the wire of a paper making machine.

We claim as our invention:

1. The method of making asbestos yarn, which comprises continuously passing forwardly an elongated mass of yieldably bonded asbestos fibers the majority of which are disposed generally parallel to each other and generally parallel to the length of the mass, retaining said mass, intermediate its travel, in the form of a web of greater width than thickness, continuously displacing adjacent fibers comprising said web longitudinally with respect to each other at a decreasing rate from the edges of said web toward its longitudinal center while laterally displacing said fibers and accumulating them adjacent the projected longitudinal axis of the web by simultaneously subjecting said web to torsion and tension.

2. The method of making asbestos yarn, which comprises continuously passing a tape composed of a web of individualized, yieldably bonded, asbestos fibers forwardly at a controlled rate between a pair of rolls while retaining it therebetween in planar form, continuously subjecting said web upon emergence from said rolls to tension and torsion to laterally and longitudinally displace ad acent fibers thereof relative to each other to cause said fibers to converge at a zone adjacent the projected longitudinal axis of the tape to form a yarn of twisted fibers.

3. The method of making asbestos yarn, which comprises continuously passing a tissue-like tape composed of a felted fibrous web of individualized, longitudinally directionalized, yieldably bonded, asbestos fibers forwardly at a controlled rate between a pair of rolls while retaining it therebetween in planar form, continuously subjecting said web upon emergence from said rolls to tension and torsion to laterally'and longitudinally displace adjacent fibers thereof relative to each other to cause said fibers to converge at a zone adjacent the projected longitudinal axis of the tape to form a yarn of twisted fibers.

4. The method of making asbestos yarn, which comprises continuously passing forwardly, in normally dry condition, an elongated mass of individualized, yieldably bonded, spinning grade length chrysotile asbestos fibers the majority of which are disposed generally parallel to each other and generally parallel to the length of the mass, retaining said mass, intermediate its travel, in the form of a web of greater width than thickness, continuously displacing adjacent fibers comprising said web longitudinally" with respect to each other at a decreasing rate from the edges of said web toward its longitudinal center while laterally displacing said fibers and accumulating them adjacent the projected longitudinal axis of the web by simultaneously subjecting said web to torsion and tension.

5. The method of making asbestos yarn, which comprises drafting a tissue-like tape composed of longitudinally directionalised, yiel I bonded, spinning grade length Chrysotile asbestosfiberstoenhanceparallelismofthecomponent fibers, continuously passing said tape forwardly at a controlled rate between a pair of rolls while retaining it therebetween in planar form, continuously subjecting said web upon emergence'from said rolls to tension and torsion to la y and longitudinally displace adjacent fibers thereof relative to each other to cause saidfibers to converge at a zone adjacent the projected longitudinal axis of the tape to form a yarn of twisted fibers.

6. The method of making asbestos yarn, which comprises continuously passing forwardly and at a controlled rate between a pair of rolls, and'm normally dry condition, a tape composed of a tissue-like, felted, fibrous web of individualized, longitudinally directionalized, yieldably bonded, asbestos fibers, said asbestos fibers being the sole fibrous component of said web and being predominantly of a diameter of from about 200 to 500 angstrom units, continuously subjecting said web upon emergence from said rolls to tension and torsion to laterally and longitudinally displace adjacent fibers thereof relative to each other to cause said fibers to converge at a zone adjacent the projected longitudinal axis of the tape'to form a yarn of twisted fibers.

1. The method of making asbestos yarn, which comprises continuously passing forwardly at a controlled rate between a pair of rolls, and in normally dry condition. a tape composed of a felted, fibrous web of individualized, longitudinally directionalized, yieldably bonded. asbestos fibers having adsorbed thereon and the web containing organic surface-active material. continuously subjecting said web upon emergence from said rolls to tension and torsion to laterally and longitudinally displace adjacent fibers thereof relative to each other to cause said fibers to converge at a zone adjacent the projected longitudinalaxisofthetapetoformayarnof twisted fibers, and subjecting said yarn to heat to pyrolytically decompose said organic material content thereof whereby to fixe said fibers in a relatively firmly bonded condition.

8. The method of making asbestos yarn, which comprises drafting a tissue-like tape composed of longitudinally directionali'zed, yieldably bonded, spinning grade length Chrysotile asbestos fibers, having adsorbed thereon and the web containing organic surface-active material comprising dioctyl sodium sulfosuccinate. to enhance parallelism of the component fibers and continuously passing said tape forwardly at a controlled rate between a pair of rolls while retaining it therebetween in planar form, continuously subjecting said web upon emergence from said rolls to tension andtorsion to laterally and longitudinally displace adjacent fibers thereof relative to each other to cause said fibers to converge at a zone adjacent the longitudinal axis of the tape to form a yarn of twisted fibers,

.tape being in relatively attenuated drafted form as compared to the center.

rzanon J. NovAK CLIFFORD w. PALM.

n-srnmzncss crrsn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,585,617 Heany May 18, 1926 1,908,472 Cannon May 9, 1933 Bird et 8.1. Dec. 29, 1942 

